Three solid metallic sphere whose radii are 3cm, x cm and 18cm respectively, are melted and recast into a single solid sphere of diameter 38cm. Then find the total surface area of the sphere with radius x cm?

A right circular cone of largest volume is cut out from a solid wooden hemisphere. The remaining material is what percentage of the volume of the original hemisphere?

The radii of three concentric circles are in the ratio of 4 : 5 : 7. What is the ratio of the area between the two inner circles to that between the two outer circles?

What is the area of an equilateral triangle having altitude equal to $$5\sqrt{3}$$cm.

What is the area ( in cm² ) of the circumcircle of a triangle whose sides are 6 cm , 8 cm and 10 cm respectively ? 

The perimeter of a circle is equal to the square perimeter. What will be the ratio of their areas?

In a circle, difference between the circumference and radius is 37 cm. Find the area (in cm²) of the circle?

The radius of a cone is 20 cm and height is 21 cm, the total surface area of the cone is in square cm: